Study On Technology Of Deep Desilication In Sodium Aluminate Solution With High Alumina Concentration Producted By Bayer Process

With the development of socio-economic and material science, chemical aluminum hydroxide and alumina are growing demand. At present, the domestic chemical alumina products in short supply, increasingly high demands on quality. Silicon is the main impurities in alumina production process and very harmful. In the Bayer production process, A/S is generally controlled at250to350, so as to satisfy the need of metallurgical grade alumina production. However, for special-purpose chemicals alumina, its impurities content is strictly controlled. Therefore, research of Bayer sodium aluminate solution with high concentration of deep desilication process can meet the need of chemicals alumina production and very meaningful.Based on the research of related literature about deep desilication process and combined with the Practical condition of alumina production process in ZhongMei aluminum industry Co, Ltd of HCCN. The deep desilication test of Bayer process high concentration sodium aluminate solution was systematic studied in the laboratory. The main research conclusions are as follows:(1) The main factors for deep desilication in sodium aluminate solution with High Alumina Concentration Producted by Bayer Process were the dosage of lime temperature and time; The mixing speed and dosage of MgO were little influence for deep desilication.(2)The temperature is the biggest impact factors for deep desilication. The A/S of sodium aluminate solution will be rised by the rise of temperature. The rise of temperature is better for deep desilication reaction. Considering the energy consumption, it is appropriate to control the temperature at105℃.(3) It deserts a prositing in effect on deep desilication process to increasing the amount of lime. As increasing the amount of lime can gradually reduce the concentration of SiO2in purified liquor, and the A/S of the purified liquor after deep desilication can significantly increased.(4)Prolong the reaction time is better for deep desilication process and the A/S of the purified liquor after deep desilication can increased. But excessive prolong the reaction time is not appropriate. On the one hand, after120min the concentration of SiO2in purified liquor is less reduced, and the more time, the greater volume of equipment needed. So the deep desilication duration time in120min is advisable.(5)The stirring speed for deep desilication in sodium aluminate solution with high alumina concentration producted by Bayer process should controlled at400rpm.(6) Increasing the amount of MgO for deep desilication effect is not obvious, but it is better for the purification of sodium aluminate solution with high concentration of bleaching effect. A large number of MgO to join will cause loss of alumina from the purified liquor. Therefore, the amount of MgO should be controlled in5g/L or so.(7) Analysis of the deep desilication slag by XRD, the main composition is garnet hydrate, Sodium alumino silicate hydrate and hydration aluminum magnesium carbonate.(8) The content of effective calcium in lime have great impact on deep desilication effect. In order to meet the needs of production, the content of effective calcium of lime should be controlled over87%.The optimized technological conditions for deep desilication in sodium aluminate solution with high alumina concentration producted by Bayer Process are as follows:the desilication temperature is105℃, the amount of lime added is22.5g/L,and desilication duration time is120min, the stirring speed is400rpm, the amount of MgO is5g/L.Through the experimental study on technology of deep desilication in sodium aluminate solution with high alumina concentration producted by Bayer process, the A/S of the purified liquor after deep desilication can reach more than700. It is better to meet the need and requirements for chemicals alumina production, and provide the reference data and application value for the enterprise industrial product.